Welcome to the third of seven articles about close quarters maneuvering. So far we have learned to wait and observed the wind as well as to use neutral as the primary transmission position. Today we will take a look at the third element mentioned in part one.—throttle position.
How much throttle and throttle position.
In general it is important to use as little throttle as possible when in close quarters. The addition of the throttle (adding power) results in increasing the boat’s momentum. The only time this is not true is if power is added to stop or slow the direction the boat is currently moving. Even then, the throttle very quickly goes from decreasing momentum to adding momentum, in whatever direction the shifter and helm are in and the results are very unpredictable.
People have the tendency, when they are frightened, to either do more of whatever they are doing or to freeze. That means that if they have just added power and the result is not what they expected they would tend to add more power or they would fail to remove the power they added. Neither of these scenarios is good.
If you remember from the first two parts in this series, the goal should be to always need to add more momentum to the boat, not try to take it away. Adding power without thoroughly thinking it through will usually result in the boat having too much momentum and then we are left with the dilemma of trying to dissipate that momentum with very little space around the boat.
With the exception of exceptional wind and or current, idle speed will get the job done. It might take a few more cycles of reverse and forward, but moving in close quarters should not be a race. Back and fill turns (standing turns to you sailors) work just fine at idle speed. As discussed in part two of this series, single inboard engine sailboats will need throttle added to compensate for their small engine and propeller size.
Understanding advance and transfer.
So, in close quarters, when is it okay to add power? Now there’s a good question! To understand the answer there are some things we need to know. Every turn made on a boat, no matter what speed we are traveling, involves two components. These components are called advance and transfer. Advance is the distance that the boat travels (regardless of what direction the bow is pointing) in the original direction before a turn was started. Transfer is the distance laterally (sideways) the boat has moved until it is established on its new course.
(Click on figure 1 to display in new window). Obviously, in close quarters we want both of these to be minimal. We would like the boat to simply pivot (no advance and transfer) from the original heading to the new heading. The only way that is possible is if warp lines are used to execute the turn or the boat is lying against a pile, using it as a pivot point. (see part seven of this series when it is published.)
Any time the boat is moving, in any direction, it has momentum. I think it was Newton that told us that a body in motion tends to stay in motion. So, if a boat is traveling forward and is then turned, the boat will still tend to travel forward as it makes the turn—advance.
However, if the boat is stationary and the helm is turned hard over in the direction of the desired turn and then shifted into forward (or reverse for directed thrust boats) there will be a brief period of time, just a couple of seconds, that the initial thrust of water against the rudder will lunge the stern of the boat in the opposite direction that the helm is turned–transfer. That period of time will quickly end and the advance of the boat will begin. In most instances idle power will be enough to get the turn done.
If there are strong winds and or current it may be necessary to add a judicious amount of power to combat those conditions. It is critical to add that power as soon as the transmission is engaged and to remove that power as soon as forward or reverse motion is detected. That means that the power is added for no more than a couple of seconds!
This action will maximize the transfer and minimize the advance. Be prepared for the stern to lunge in the direction opposite the helm and for the bow to turn in the direction we want to go. It is also critical to remember where the boat’s pivot point is. On keel sailboats that point is directly over the keel. For power boats of all types that point is 25-30 percent forward of the stern. Here lies the first hazard of adding power.
If the stern of our boat is NOT clear of the dock, pilings, or other boats the power added will drive the stern into those objects. NOT GOOD! If the helm is not pointed in the direction we want to go BEFORE the transmission and throttle are engaged the stern will not lunge in the direction we want. It will lunge in the direction opposite the helm position. If we delay in adding the power then advance will not be minimized. It is easier for the boat to advance then transfer. By adding power immediately we force the boat to twist in the turn rather than move forward. This advantage only last for a few seconds before the boat starts its advance.
Throttle and twin-engines.
Let’s talk about twin-engine propulsion systems. I know that most people that have not had formal instruction get behind the helm and when in close quarters split the engines (operate one engine in forward and the other in reverse). I also know that they start adding power to one or both (YIKES) engines. I’m here to tell you that sooner or later this will result in an insurance claim. Before they know it they have both engines running at about 5,000 RPM. The water gets so full of air and turbulence that the boat loses buoyancy and may sink! (Okay, the last sentence was a little over the top, but my point is made.)
There is no need to have both engines engaged at the same time, other than being impatience. Sure we should split the engines, but only one engine should be engaged at a time; and that engine should be at idle speed. Twin-engine inboard boats rely on the asymmetric thrust (the engines not being near the center-line of the boat) to reap the close quarters maneuvering advantage. By always engaging the out-board engine during a turn the boat is able to pivot around the stern corner of the boat on the inside of the turn. Remember, if we want to rotate the boat to port then when in forward the port stern corner is on the inside the turn and the stern is pivoting counter-clockwise, but when in reverse, the starboard stern corner is on the inside of the turn and the stern is still rotating counter-clockwise.
Generally no helm or throttle inputs are necessary. If there is strong wind or current than throttle may be required, but only for the part of the turn that involves pushing the bow into the wind or current. When pushing the bow into wind and or current the cycle of shifts should be rapid. Always pause in neutral between shifts, but don’t delay. Once the bow is being pushed downwind or down current then only idle speed should be used.
If our twin-engine boat has directed thrust than all of the above still applies but the helm should be swung from side to side just before we shift from forward to reverse or vice-versa. It is advantageous to swing the helm since twin outboard engines are generally located much closer to the centerline of the boat—affording less leverage. Always get the helm hard over prior to shifting into gear and or applying power. Always complete the helm swing with urgency while in neutral. We are trying to build twisting momentum and the longer we delay between shifts the longer the wind and or current have to stop our momentum.
A practical example of throttle position.
Let’s look at an example (click on figure 2 to open in new window). Joe is on a single engine inboard trawler with a right hand prop (prop rotation is clockwise in forward). He wants to leave his slip and turn to starboard into the fairway. He is stern into the slip. Joe’s first move after releasing all of his lines is to clutch (shift) into forward at idle speed. He does this just long enough to get the boat moving forward; then he shifts back to neutral.
He has his helm basically neutral although he steers slightly as needed to keep his boat going straight, avoiding the dock and piles. As soon as the boat’s stern will clear all obstacles Joe moves the helm to full starboard then clutches to reverse for a few seconds. This action will induce prop walk, the tendency for the prop to pull the boat’s stern laterally in the direction of prop rotation, and the stern will be pulled to port swinging the bow to starboard. This shift to reverse has the added benefit of stopping the remaining forward momentum. He now shifts to neutral and pauses. Leaving the helm to starboard he next shifts to forward. The prop is now pushing a wall of water at the rudder, which is still hard to starboard. He has added prop wash (water washing against the turned rudder) and the boat will continue its rotation clockwise–starboard. Next, he shifts back to neutral, pauses to evaluate his rotation, and then back to reverse. He continues this cycle until the bow is pointed nearly at his desired heading—approximately 90 degrees to starboard. Now he simply drives down the fairway.
If there was wind from the starboard side he may need to add some power to each of the above steps (click on figure 3 to open in new window). The power added will accentuate prop walk–a good thing in this case. In forward the added power increases prop wash; more power means more water against the rudder and therefore more twist, but it also means more advance—something he DOES NOT want. The power added should be immediate, fast, and very short lived.
If there was no wind or wind from port then there would be NO need for any added throttle. He would need to repeat the cycle of shifts more times when trying to push the bow into the wind or current.
Truth be told, if there were that much wind Joe would be much better off coming out of the slip and turning to port, downwind, and back out the fairway with his stern to the wind.
Just a couple of notes:
- Adding power always results in advance (regardless of forward or reverse)
- Adding power always increases momentum. In the case of turning, only part of that momentum is in the direction that you want.
- Power maybe necessary in the following instances:
- Pushing the bow into the current or wind
- Single engine inboard keel sailboats
- Momentary power may be necessary in the following instances: a. To increase the rate of turn (decrease the radius)
- When in close quarters we want to decrease advance and transfer
- Proper helm position along with judicious power can help to lunge the stern of the boat past an object such as a piling or dock corner
- Proper helm position along with proper transmission position can move the stern of the boat closer to the dock enabling a crew member to step off the boat
- Props and rudders are much more effective in forward than reverse
- Prop walk cannot be wished away. However, by NOT using throttle we can minimize it and by using throttle we can maximize it. Be sure to contemplate this before you do it.
- As mentioned in part one and part two remember that as you are maneuvering the boat, wind and current are still pushing you in their respective directions.
- Practice these techniques in open water first. As you master them move into increasingly tighter quarters.
- Power adds momentum. If contact with surrounding obstacles is going to occur then more momentum always makes more damage. STAY OUT OF THE THROTTLE
The best way to develop and master knowledge of throttle position and all of these skills is with me! On the Water…With Captain Frank